A MMP‐independent role for TIMP‐2 during cardiac neural crest cell migration

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Tissue inhibitor of metalloproteinase‐2 (TIMP‐2), a matrix metalloproteinase (MMP) inhibitor, is uniquely expressed in cardiac neural crest (NC) cells. Blocking TIMP‐2 synthesis perturbs NC migration while synthetic MMP inhibitors have little effect suggesting TIMP‐2 operates independent of MMP. TIMP‐2 can mediate growth factor‐induced responses independent of MMP inhibition by binding α3ß1 integrins. Here, we compared the effects of wild‐type TIMP‐2, a non‐MMP inhibiting form of TIMP‐2 (Ala+TIMP‐2), and a TIMP‐2/integrin blocking peptide on NC migratory behavior. Ala+TIMP‐2 increased NC cell motility, increased the distance NC cells migrated from neural tube explants, and altered NC cell shape (the cells were flatter and more arborized) compared to control cultures. Wild‐type TIMP‐2 also increased NC motility but had no effect on the distance NC cells migrated nor on their cell shape. A TIMP‐2/integrin inhibitory peptide had no effect on basal NC migration but it blocked the effects of Ala+TIMP‐2 in vitro and perturbed NC migration when injected into embryos. In addition, α3 integrin protein was expressed by the ectoderm, neural tube, and NC cells in situ. These data suggest TIMP‐2's functional role in NC migration may be mediated through α3ß1 integrin signaling rather than inhibiting MMP activity. Supported by the American Heart Association, Heartland Affiliate (#0555683Z) and NIH (#P20‐RR016469).